Device and method for detecting and counting articles, released by a feeder device, in particular sheet articles released by a sheet feeder

ABSTRACT

A method and device for detecting and counting articles released by a feeder device, in particular sheet articles released by a sheet feeder are described. 
     The device comprises: an electromagnetic resonator ( 11 ) fed by a signal generator ( 12 ), to generate an electromagnetic field in a passage region ( 9 ) of said sheet articles ( 3 ); a sensor ( 13 ) connected to the electromagnetic resonator ( 11 ) for detecting the induced disturbances in the electromagnetic field following the passage of one or more superimposed sheet articles ( 3 ); and a control unit ( 14 ) connected to the sensor ( 13 ) for calculating the number of sheet articles ( 3 ), which pass from time to time across the passage region ( 9 ). In particular, the electromagnetic resonator ( 11 ) is of recess type and in it an aperture ( 7 ) is made which makes said recess ( 8 ) communicating with the outside; whereby the resonator ( 11 ) is arranged so that the aperture ( 7 ) is disposed at the passage region ( 9 ). 
     The method comprises the steps of: intermittently releasing sheet articles by the feeder ( 10 ); conveying the sheet articles ( 3 ) across the passage region ( 9 ); detecting the disturbances induced in the electromagnetic field after the passage of one or more superimposed sheet articles ( 3 ); calculating the number of sheet articles ( 3 ) which pass from time to time across the passage region ( 9 ) according to the measurements carried out in the preceding step.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the technical field of packaging machines of piles of sheet articles, for example of paper documents, inserts or the like, which piles, when packaged, are intended to be sent by post; in particular, the invention relates to devices for detecting and counting the sheet articles released by feeder devices, included in the same packaging machines.

DESCRIPTION OF THE ART

A known packaging machine of the above-described type comprises: a conveyor member, which, by means of shaped strikers, spaced at a predetermined distance, moves corresponding article piles forming in an advancement direction; a first feeder device arranged upstream of the conveyor member, which above the latter, intermittently releases a sheet article at the time (that is a magazine, a bundle or the like) intended to be intercepted by a corresponding shaped striker; a plurality of feeder devices arranged in cascade along the development of the conveyor member to release, in suitable phase relation and above the latter, respective sheet articles (sheet articles, as for example paper inserts or the like) in order to progressively form piles in advancement; and a station, arranged downstream of the conveyor member, for packaging the thus formed piles, for example for their introduction in envelopes or their winding by means of a film or sheet, of plastic or paper respectively.

According to a diffused structural configuration, a feeder device comprises two endless belt conveyors, mutually arranged to provide as many active counter-faced branches, a lower and an upper one, intended to drag gripped sheet articles towards an output section communicating with said conveyor member; in particular the upper conveyor has the driven gear, defined by a much greater dimensioned drum than that of the remaining driving gears, driven gears and snub pulleys and is provided with suction means intended to take an article at the time from the base of a thereon arranged pile, which is integral to the frame of the feeder, according to known ways, and to drag the article until the two counter-faced branches, which extend partially around a section of the lower profile of the same drum, grip it.

Such feeder device is associated with means, which interact with a determined lower portion of such counter-faced branches, which is in contact with the drum, these means being intended to detect the passage of none, one or more superimposed sheet articles; their control function being aimed at the generation of an error signal in case instead of a single sheet article, no sheet article passes or two or more superimposed sheet articles pass. Usually, these control means comprise: a mechanic amplifier, which interacts with said belt portion of the lower conveyor, intended to induce a rotation of one detecting arm of its own, proportionally to the shifting undergone by the same belt portion, after the passage of one or more sheet articles; a proximity sensor, sighting a direction perpendicular to the area interested by the same arm and interfering with the latter. The mechanic amplifier can be for example a shaft, rotatably carried on the frame of the feeder device, constrained on one side at a transversal detecting arm and on the other one at a little arm, which on the opposing end, comprises an idle roller (so-called “feeler”), which rolls on said belt portion of the lower conveyor and is in contact thereon by means of elastic means, interposed between the same little arm and the frame. Therefore, following the passage of a sheet article above the belt portion intercepted by the roller, the detecting arm carries out a temporary rotation from a stable rest position to a first angular position, carrying out an excursion as much marked as greater the thickness of the passing article is; when the passage is ended, the detecting arm comes back to its original, stable balancing position.

The sensor is disposed such that its optic beam sights the detecting arm when the latter is stable in the first angular position, in order to break the light beam, for a minimum predetermined time, only when a sheet article passes. A local computer unit, for example associated to the feeder device, receives the signals supplied by the proximity sensor; by way of example it can define an error state, to which the production stop might follow, if, when a sheet article is required to the output of the feeder, the relative signal generated by the proximity sensor, indicating the passage of a single sheet article in a determined time, does not correspond. A similar solution is very diffused in this field, even if it implies many drawbacks: sheet articles of relevant thickness (therefore, for example more than sixty micrometers), in fact, determine remarkable mechanic stresses on the mechanic amplifier, defining an upper limit of the operative speed of the feeder and therefore of the productivity of the packaging machine in which the latter is integrated; moreover, such limit, has to be further reduced to allow the same amplifier to withstand stress “peaks”, which are induced by the undesired passage of two or more superimposed sheet articles between the counter-faced branches. The position of the sensor emitted light beam has also to be adjusted every time a format change of the loaded articles in the feeder device is required, as a thickness variation of the passing article between the counter-faced branches corresponds to a different angular excursion of the detecting arm; clearly, this operation requires expert personnel, a great number of technical tests, suitable devices and a remarkable time in comparison to the pressing requirements of a productivity, which is higher and higher. Moreover, the required adjusting times increase according to the total number of feeder devices associated to the conveyor member (being not possible the usage of an operator and the required equipment for every conveyor, for obvious cost reasons), and become therefore unsustainable as the packaging machine becomes more complex.

Generally, it can be said that the devices for detecting and counting sheet articles released by feeder devices are disadvantageous because they are subjected to detecting errors and because they define, in order to properly function, a significant limit to the productivity of the packaging machine.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a device for detecting and counting sheet articles, intermittently released by a feeder device, which is able to satisfactorily solve the above-mentioned drawbacks, peculiar to the known solutions; so it is intended to provide a newly designed device, which is reliable, precise, functional, compact and which can be easily integrated inside feeder devices of known type as well, and whose costs are relatively reduced with respect to the advantages, which it is intended to pursue.

Another object of the present invention is to provide a method for detecting and counting sheet articles, intermittently released by a feeder device which is able to satisfactorily solve the above-mentioned drawbacks, peculiar to the known solutions; so it is intended to provide a newly designed method, distinguished by an essential number of operating steps, which allows to precisely and reliably detect and count the sheet articles released by a feeder device and whose implementation costs are relatively reduced with respect to the advantages, which it is intended to pursue.

Said above-mentioned objects are accomplished by a device and a method according to claims 1 and 7, respectively.

The device for detecting and counting sheet articles released by a feeder device, in particular sheet articles released by a sheet feeder, is characterized in that it comprises: an electromagnetic resonator fed by a first signal supplied by a signal generator, to generate an electromagnetic field in a passage region of said sheet articles; a sensor connected to the output of said electromagnetic resonator for detecting a second signal which identifies the induced disturbances in said electromagnetic field following the passage of said one sheet article or the passage of a plurality of said superimposed sheet articles; and a control unit connected to said sensor for calculating the number of said sheet articles, which pass from time to time across said passage region.

In a dependent claim, it is précised that the electromagnetic resonator is a resonator of recess type, in which it is made an aperture which makes this recess communicating with the outside and that said electromagnetic resonator is arranged such that said aperture is disposed at said passage region of said sheet articles.

The method for detecting and counting articles released by a feeder device, in particular sheet articles released by a sheet feeder, is characterized in that it comprises the following operating steps: intermittently releasing sheet articles by said feeder device; conveying said sheet articles, thus released, across a passage region in which a predetermined electromagnetic field acts; detecting the disturbances induced in said electromagnetic field after the passage of said one sheet article or after the passage of a plurality of said superimposed sheet articles; calculating the number of said sheet articles, which pass from time to time across said passage region according to the measurements carried out in the preceding step.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention, not emerging from the preceding description, will be better highlighted in the following, according to the claims and by means of the appended drawings, in which:

FIG. 1 shows a side schematic view of a feeder device of known type, in which the inventive device for detecting and counting sheet articles is integrated;

FIG. 2 shows a functional scheme of the device for detecting and counting of FIG. 1;

FIG. 3A shows the recess electromagnetic resonator shown in FIG. 1, while FIG. 3B shows a variant thereof;

FIG. 4A shows an illustrative graph of the amplitude according to the frequency of a signal emitted by the electromagnetic resonator, the graph representing three curves, relative to as many functioning configurations indicated by #0, #1, #2 (no sheet article passing, one sheet article passing, two superimposed sheet articles passing; respectively);

FIG. 4B shows an illustrative graph of the phase displacement according to the frequency of a signal emitted by the electromagnetic resonator, the graph representing three curves, relative to as many significant functioning configurations indicated by #0, #1, #2 (no sheet article passing, one sheet article passing, two superimposed sheet articles passing; respectively).

DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1, by the reference number 10 is indicated in its entirety a feeder device of known type, substantially of the above-described type, in which the inventive device 100 for detecting and counting sheet articles is integrated.

The shown feeder device 10 comprises two endless belt conveyors 1, 2, mutually arranged to provide as many active counter-faced branches, a lower one 21 and an upper one 22, intended to drag gripped sheet articles 3 towards an output section U communicating with said conveyor member (not shown) of the packaging machine (also not shown as not relevant to the invention); in particular, the upper conveyor 1 has the driven gear, defined by a much greater dimensioned drum 4 than that of the remaining driving gears, driven gears and snub pulleys and is provided for example with gripping means (not shown) intended to take an article 3 at the time from the base of a thereon arranged pile 5, which is integral to the frame 6 of the feeder 10, according to known ways, and to drag the article until the two counter-faced branches 21, 22, which extend partially around a section of the lower profile of the same drum 4, grip it.

The inventive detecting and counting device 100 is functionally disposed at a section of the path, which is run by each sheet article 3 released from the pile 5 and moved towards the output section U, according to ways, which will be better described in the following; in the example shown in FIG. 1, the device 100 is fixed at the frame 6 and arranged upstream of the counter-faced branches 21, 22 of the two belt conveyor 1, 2.

The detecting and counting device 100 comprises an electromagnetic resonator 11 of recess type, in which it is made an aperture 7, which makes the same recess 8 communicating with the outside; the electromagnetic resonator 11 is so positioned that the aperture 7 is arranged at a region 9 which is provided immediately upstream of the counter-faced branches 21, 22 and in which the sheet articles 3, conveyed towards the output section U of the feeder 10 are destined to pass. In general, however, the electromagnetic resonator 11 can be arranged in any section of the path run by the sheet articles 3 released from the pile 5 and conveyed towards the output section U of the feeder 10; as a particular case, the resonator 11 can be functionally interposed between the output section U and the conveyor member of the packaging machine, that is to say, outside the feeder 10.

The inventive device 100 comprises also: a signal generator 12 which supplies the electromagnetic resonator 11 with a signal S1 to define an electromagnetic field in the recess 8 and in the aperture 7 coinciding with the passage region 9; a sensor 13 connected to the output of said electromagnetic resonator 11 to detect a signal S2 which identifies the induced disturbances in the electromagnetic field following the passage in the passage region 9 of a sheet article 3 or of a plurality of superimposed sheet articles 3; an analogue-to-digital converter 15 for converting in digital format the analogue signal supplied by the sensor 13; and a control unit 14 connected to the signal generator 12 and to the analogue-to-digital converter 15, which controls the functioning of the detecting and counting device 100 in its entirety and which is connected to other not shown outer units, for example a control panel for the operator and/or electromechanical apparatuses of the packaging machine.

The signal generator 12 comprises for example oscillating electronic circuits and/or numerical control circuits DDS (Direct Digital Synthesizer) and supplies the high frequency signal 51 having a frequency between 1 MHz and 100 GHz, at the input of the electromagnetic resonator 11.

By way of example, the sensor 13 is instead a detector device, which converts the high frequency signal S2 received by the electromagnetic resonator 11 in two signals in direct current (DC), whose values vary according to the amplitude (power) and to the phase of the same signal S2.

In the appended drawings, various illustrative embodiments of the recess electromagnetic resonator 11 are shown; in FIGS. 1, 3B the electromagnetic resonator 11 extends in longitudinal direction, has a rectangular transversal section, and the aperture 7 is made according to the relative longitudinal development dividing the same resonator 11 in two distinct and counter-faced portions 16, 17; FIG. 3A shows another example of the electromagnetic resonator 11, with a cylindrical configuration, also distinguished by the aperture 7 made according to the longitudinal development dividing the same resonator 11 in two distinct and counter-faced portions 16, 17; in the schematic representation of FIG. 2, the electromagnetic resonator 11 in instead similar to the one represented in FIGS. 1, 3B but it is different in that it is an unique body with the aperture 7 of predetermined depth. The recess 8 of the electromagnetic resonator 11 can be for example interested by air or Teflon.

The functioning of the inventive detecting and counting device 100 is based on detecting the disturbance of the electromagnetic field acting in the aperture 7, which as said, thanks to the suitable arrangement of the recess electromagnetic resonator 11, coincides with the passage region 9 of the sheet articles 3. Such disturbance of the electromagnetic field is caused by the passage of a sheet article 3 across the passage region 9 or of more superimposed sheet articles 3 which, by mistake, have been drawn from the base of the pile 5 of the feeder 10.

Therefore, the aperture 7 is so shaped and dimensioned to allow the passage of one or more superimposed sheet articles 3 and to define a predetermined electromagnetic field in order to detect the passage of said sheet articles 3.

The functioning of the inventive detecting and counting device 100 results generally from the following description of the method for detecting and counting sheet articles 3, intermittently released by the feeder device 10, also object of the invention, the method comprising the following operating steps:

-   -   a. intermittently releasing sheet articles 3 from the pile 5 of         the feeder device 10;     -   b. conveying the sheet articles 3 across the passage region 9 in         which a predetermined electromagnetic field defined by the         signal generator 12 acts;     -   c. detecting the disturbances induced in this electromagnetic         field after the passage of said one sheet article 3 or after the         passage of a plurality of superimposed sheet articles 3;     -   d. calculating the number of sheet articles 3, which pass from         time to time across the passage region 9 according to the         measurements carried out in the preceding step.

In the following, it will be described in further detail one among the possible functioning ways of the detecting and counting device 100, object of the present invention.

FIG. 4A shows an illustrative graph of the amplitude variation of the signal S2 according to the frequency, when at the input of the electromagnetic resonator 11 is applied a signal S1 of prefixed amplitude and phase: the graph shows three curves indicated by #0, #1, #2, which represent the different behaviour of the electromagnetic resonator 11 in case in the passage region 9 no sheet article 3 passes (curve #0), only one sheet article 3 passes (curve #1) or two superimposed sheet articles 3 pass (curve #2). As it can be noted, these curves run in a “bell-like” way, which is peculiar to an electromagnetic resonator, which “resounds” at the frequency (resonance frequency), centred with respect to the corresponding reference curve.

FIG. 4B allows similar considerations. It shows an illustrative graph of the phase variation of the signal S2 according to the frequency when at the input of the electromagnetic resonator 11 is applied a signal S1 of prefixed amplitude and phase; in fact, the graph shows three curves indicated by #0, #1, #2, which represent the different behaviour of the electromagnetic resonator 11 in case in the passage region 9 no sheet article 3 passes (curve #0), only one sheet article 3 passes (curve #1) or two superimposed sheet articles 3 pass (curve #2).

F₀ indicates the resonance frequency of the “loadless” electromagnetic resonator (no sheet article 3, curve #0); the praxis suggests to choose the frequency F_(S) of the signal S1 preferably between F₀−5*F₀/Q₀ and F₀+5*F₀/Q₀, where Q₀ is the merit factor of the electromagnetic resonator 11 when in the passage region 9 there is no sheet article 3 passing.

The graphs shown in FIGS. 4A, 4B define: A₀(F_(S)), P₀(F_(S)) respectively as amplitude and phase of the signal S2 when there are no sheet articles 3 in the passage region 9; A₁(F_(S)), P₁(F_(S)) as amplitude and phase of the signal S2 when there is only one sheet article 3 in the passage region 9; A₂(F_(S)), P₂(F_(S)) as amplitude and phase of the signal S2 when there are two sheet articles 3 in the passage region 9.

It is possible to define the attenuation and the phase displacement undergone by the signal S2 when only a single sheet article 3 passes in the passage region 9, as:

ΔA₁(F_(S))=|A₀(F_(S))−A₁(F_(S))|

ΔP₁(F_(S))=|P₀(F_(S))−P₁(F_(S))|

and the attenuation and the phase displacement undergone by the signal S2 when two superimposed sheet articles 3 pass in the passage region 9, as:

ΔA₂(F_(S))=|A₀(F_(S))−A₂(F_(S))|

ΔP₂(F_(S))=|P₀(F_(S))−P₂(F_(S))|

In general terms, the attenuation and the phase displacement undergone by the signal S2 can be instead defined as:

ΔA_(L)(F_(S))=|A₀(F_(S))−A_(L)(F_(S))|

ΔP_(L)(F_(S))=|P₀(F_(S))−P_(L)(F_(S))|

where A_(L)(F_(S)), P_(L)(F_(S)) are respectively the amplitude and the phase of the signal S2 detected at the frequency F_(S) after the passage of zero, one, two or more superimposed sheet articles 3 in the passage region 9.

When the attenuation ΔA₁(F_(S)), ΔA₂(F_(S)) undergone by the signal S2, in case of passage of one sheet article 3 or of two superimposed sheet articles 3 respectively in the passage region 9, is known, it is possible to provide suitable threshold values TA_(L), TA_(H) with TA_(L)<TA_(H) so that:

-   -   if ΔA_(L)(F_(S)) is greater than the lower threshold TA_(L) and         smaller than the upper threshold TA_(H), there is a sheet         article 3 in the passage region 9;     -   if ΔA_(L)(F_(S)) is smaller than the lower threshold TA_(L)         there are no sheet articles 3 in the passage region 9;     -   if ΔA_(L)(F_(S)) is greater than the upper threshold TA_(H),         there are at least two superimposed sheet articles 3 in the         passage region 9, whereby a drawing error of the sheet articles         3 from the base of the pile 5 is detectable.

Similarly, when the phase displacement ΔP₂(F_(S)), ΔP₁(F_(S)) undergone by the signal S2, in case of passage of one sheet article 3 or of two superimposed sheet articles 3 respectively in the passage region 9, is known, it is possible to provide suitable threshold values TP_(L), TP_(H) with TP_(L)<TP_(H) so that:

-   -   if ΔP_(L)(F_(S)) is greater than the lower threshold TP_(L) and         smaller than the upper threshold TP_(H), there is a sheet         article 3 in the passage region 9;     -   if ΔP_(L)(F_(S)) is smaller than the lower threshold TP_(L)         there are no sheet articles 3 in the passage region 9;     -   if ΔP_(L)(F_(S)) is greater than the upper threshold TP_(H)         there are at least two superimposed sheet articles 3 in the         passage region 9, whereby a drawing error of the sheet articles         3 from the base of the pile 5 is detectable.

Every above-described calculating operation can be carried out by the control unit 14 according to the data supplied by the detector device 13 by means of the analogue-to-digital converter 15 (which can be alternately integrated in the same control unit 14).

From the preceding description it results clear that for detecting and counting the sheet articles 3 passing across the passage region 9, it is sufficient to consider even only amplitude or phase detecting of the signal S2, from which then it is possible to go back respectively to the attenuation and the phase displacement of the same signal S2. In this way, the detector device 13 can be alternately chosen to supply only a signal emitted in direct current (DC), whose values vary according to the amplitude or the phase of the signal S2.

In order to carry out the above-described operations, which allow to count the number of sheet articles 3 passing across the passage region 9, it is required to have preliminary measures of amplitude and/or phase of the signal S2 at the pre-chosen frequency F_(S) at one's disposal, in case of no sheet articles passing (values A₀(F_(S)), P₀(F_(S))), only one sheet article 3 passing (values A₁(F_(S)), P₁(F_(S))) and two superimposed sheet articles 3 passing (values A₂(F_(S)), P₂(F_(S))); the knowledge of these values allows then to define the above-mentioned thresholds of amplitude TA_(L), TA_(H) and frequency TP_(L), TP_(H).

In practical terms, the control unit 14 can carry out an amplitude and phase measurement of the signal S2 at the pre-chosen frequency F_(S) only one time, with no sheet articles 3 passing in the passage region 9, storing the values A₀(F_(S)), P₀(F_(S)); in the event of a format change of the sheet articles 3, it is for example sufficient that by means of a control panel (not shown) the operator controls at the control unit 14 the running of an acquisition preliminary phase during which a sheet article 3 according to the new format is released from the pile 5, so that the control unit 14 itself can store the new values A₁(F_(S)), P₁(F_(S)). It has to be précised that in the event of a format change of the sheet articles 3, in which material and/or dimensions and/or thickness of the same sheet articles 3 change, the curve indicated by #1 in the graphs of FIGS. 4A, 4B can undergo even sensible variations, that have to be considered in order to count the sheet articles 3.

The values A₁(F_(S)), P₁(F_(S)) associated to every type of sheet articles 3 can result pre-loaded in the storage of the control unit 14 or can be stored from time to time in the event of a format change, by carrying out the starting acquisition phase; in such case, from the control panel the operator can select the new pre-chosen format by a list of available formats or can control said acquisition phase.

This is extremely advantageous because it makes very easy and fast the format change operation of the sheet articles 3, which can be carried out by means of essential controls given by the control unit 14 by means of a standard user-interface connected to the latter, as for example the above-mentioned control panel; skilled personnel manual interventions to adjust mechanical portions of the detecting and counting device 100 are therefore not required.

The values A₂(F_(S)), P₂(F_(S)) can be determined: by means of a further acquisition phase, in which two superimposed sheet articles 3 according to the new format pass; or by means of a calculus algorithm based on the yet acquired values A₁(F_(S)), P₁(F_(S)). However, it is to be précised that these values A₂(F_(S)), P₂(F_(S)) are not indispensable to determine the thresholds of amplitude TA_(L), TA_(H) and frequency TP_(L), TP_(H).

In general terms, the control unit 14 can also provide different functioning ways of the device 100 in order to detect and count the sheet articles 3, and so to carry out more complex calculus algorithms, based for example on detecting a plurality of amplitude and/or phase values of the signal S2 for corresponding value of frequency between F₀−5*F₀/Q₀ and F₀+5*F₀/Q₀.

According to the claims, it is eventually to be précised that in order to accomplish the present invention, in the device 100, electromagnetic resonators different from those of “recess” type can be used, which are shown in the appended drawings.

The present invention is advantageous in that it defines a device for detecting and counting sheet articles, intermittently released by a feeder device which satisfies the prefixed objects, brilliantly solving every drawback lamented in the introduction, peculiar to the known devices; therefore, it has been defined a reliable, precise, compact, versatile device which can be easily integrated inside feeder devices of known type as well and whose costs are relatively reduced with respect to the achieved advantages.

The thus defined detecting and counting device has therefore the function of constantly monitoring the correct functioning of the sheet feeder 10; in case of wrong releasing of more superimposed sheet articles 3 from the pile 5 of the feeder 10, such device 100 detects a wrong condition. By way of a not limiting example, after such a wrong condition, processed by the control unit 14, a corresponding error signalling to the central processing unit of the packaging machine, an error signalling on the control panel and/or the emission of an acoustic signal can follow.

The present invention is further advantageous in that it defines a method for detecting and counting sheet articles, intermittently released by a feeder device which satisfies the prefixed objects, brilliantly solving every drawback lamented in the introduction, peculiar to the known devices; therefore it has been defined a newly designed method distinguished by an essential number of operating steps, which allows to precisely and reliably detect and count the sheet articles released by a feeder device and whose implementation costs are relatively reduced with respect to the achieved advantages.

It is intended that the preceding description is purely exemplary and not limiting, therefore possible practical-applicative variations are intended to fall into the protective scope of the invention, as defined by the following claims. 

1. Device for detecting and counting articles released by a feeder device, in particular sheet articles released by a sheet feeder, characterized in that it comprises: an electromagnetic resonator (11), fed by a signal (S1)supplied by a signal generator (12) to generate an electromagnetic field in a passage region (9) of said sheet articles (3); a sensor (13) connected to the output of said electromagnetic resonator (11)for detecting a signal (S2) which identifies the induced disturbances in said electromagnetic field following the passage of said one sheet article(3)or of a plurality of said superimposed sheet articles (3);and a control unit(14)connected to said sensor (13) for calculating the number of said sheet articles (3) passing from time to time across said passage region (9).
 2. Device according to claim 1, characterized in that said electromagnetic resonator (11) is a resonator of recess type, in which an aperture (7)is made, which makes said recess (8) communicating with the outside and in that said electromagnetic resonator (11) is arranged such that said aperture (7) is disposed at said passage region (9) of said sheet articles (3).
 3. Device according to claim 2, characterized in that said aperture (7) divides said recess resonator (11) in two distinct and counter-faced portions (16, 17).
 4. Device according to claim 1, characterized in that said sensor (13) is a detector for detecting the amplitude or power of said signal (S2) provided at the output of said electromagnetic resonator (11).
 5. Device according to claim 1, characterized in that said sensor (13) is a detector for detecting the phase of said signal (S2) provided at the output of said electromagnetic resonator (11).
 6. Device according to claim 1, characterized in that said signal generator supplies said one signal (S1), having a frequency between 1 MHz and 100 GHz at the input of said electromagnetic resonator (11).
 7. Method for detecting and counting articles released by a feeder device, in particular sheet articles released by a sheet feeder, characterized in that it comprises the following operating steps: a. releasing said sheet articles (3) by said feeder device (10); b. conveying said sheet articles (3),thus released, across a passage region (9) in which a predetermined electromagnetic fieldacts; c. detecting the disturbances induced in said electromagnetic field after the passage of said one sheet article(3) or the passage of a plurality of said superimposed sheet articles (3); d. calculating the number of said sheet articles (3), which pass from time to time across said passage region (9) according to the measurements carried out in the preceding step.
 8. Device according to claim 2, characterized in that said sensor (13) is a detector for detecting the amplitude or power of said signal (S2) provided at the output of said electromagnetic resonator (11).
 9. Device according to claim 2, characterized in that said sensor (13) is a detector for detecting the phase of said signal (S2) provided at the output of said electromagnetic resonator (11). 